diff --git a/similar/editor/elight.cpp b/similar/editor/elight.cpp
index 7ece7b578..fe075cf5e 100644
--- a/similar/editor/elight.cpp
+++ b/similar/editor/elight.cpp
@@ -151,8 +151,11 @@ static void propagate_light_intensity(const vsegptr_t segp, int sidenum)
 int LightAmbientLighting()
 {
 	range_for (const auto seg, highest_valid(Segments))
+	{
+		const auto &&segp = vsegptr(static_cast<segnum_t>(seg));
 		for (int side=0;side<MAX_SIDES_PER_SEGMENT;side++)
-			propagate_light_intensity(&Segments[seg], side);
+			propagate_light_intensity(segp, side);
+	}
 	return 0;
 }